1. Field of the Disclosure
This disclosure relates generally to a high power fiber laser amplifier and, more particularly, to a high power fiber laser amplifier that couples ends of the fiber amplifiers into a tapered fiber bundle to combine the beams with improved fill factor.
2. Discussion of the Related Art
High power laser amplifiers have many applications, including industrial, commercial, military, etc. Designers of laser amplifiers are continuously investigating ways to increase the power of the laser amplifier for these applications. One known type of laser amplifier is a fiber laser amplifier that employs doped fibers and pump beams to generate the laser beam. Typically, a high power fiber laser amplifier uses a fiber that has an active core diameter of about 10-20 μm or larger. Modern fiber laser amplifier designs have achieved single fiber power levels up to 5 kW. Some fiber laser systems employ multiple fiber laser amplifiers and combine them in some fashion to higher powers.
A design challenge for fiber laser amplifiers is to combine the beams from each fiber in a coherent manner so that the beams provide a single beam output having a uniform phase over the beam diameter such that the beam can be focused to a small focal spot. Focusing the combined beam to a small spot at a long distance (far-field) defines the beam quality of the beam, where the more coherent the individual fiber beams the more uniform the combined phase and better the beam quality. Improvements in fiber laser amplifier designs increase the output power and coherency of the fiber beams in such a way as to approach the theoretical power and beam quality limit of the laser system.